Flat iron? (4)
I believe the answer is:
even
I believe this clue is a double definition.
'flat' is the first definition.
(level)
'iron?' is the second definition.
(I've seen this before)
(Other definitions for even that I've seen before include "no-win situation?" , "draw" , "When darkness starts to fall" , "Going so far as to" , "(Of a number) divisible by 2" .)